An executive at another large automaker said his company was considering joining the agreement because it includes meaningful concessions by California. The executive, who spoke on condition that neither he nor his company be identified, said that the Obama-era fuel economy standards were difficult for the industry to meet because car buyers increasingly prefer sport utility vehicles and pickup trucks that tend to have much lower fuel economy than sedans.

Four of the world’s largest automakers have struck a deal with California to reduce automobile emissions, siding with the state, and against President Trump, in a bitter fight over one of the president’s most consequential regulatory rollbacks.

In coming weeks, the Trump administration is expected to all but eliminate a signature Obama-era regulation designed to reduce vehicle emissions that contribute to global warming. However, California and 13 other states have vowed to keep enforcing the stricter rules, potentially splitting the United States auto market in two, with car companies forced to build different lineups of vehicles for different states.

The prospect of that nightmare scenario for automakers spawned secretive talks in recent weeks between California regulators and four auto giants — Ford Motor Company, Volkswagen of America, Honda and BMW — in which the automakers won slightly less restrictive rules that they can apply to vehicles sold nationwide.

The agreement provides “much-needed regulatory certainty,” the companies said in a joint statement, while enabling them to “meet both federal and state requirements with a single national fleet, avoiding a patchwork of regulations.”

In an escalation in the fight against climate change and the Trump administration, California regulators approved new measures to defend the state’s vehicle emissions standards and bolster rules to cut carbon pollution from transportation.

The state Air Resources Board voted Friday to require automakers to comply with California’s strict rules on car and truck pollution if they want to sell vehicles in the state. It’s California’s latest move against the Trump administration’s plan to freeze fuel economy targets and revoke California’s power to set its own standards. State officials said the counterstrike was necessary to close a potential loophole automakers could use to evade compliance with California’s more stringent rules.

“The health of our state, our nation and the globe are at stake, and that is a fight worth having,” said state Sen. Ricardo Lara (D-Bell Gardens), who sits on the board.

The measure seeks to strengthen California’s footing as it fights to preserve its emissions rules, both in court and in negotiations with the White House. At the same time, the move brings the nation one step closer to having two different standards: One for California and the dozen other aligned states that account for one-third of the U.S. auto market, and another for the rest of the country.

During the board’s meeting in Sacramento, the 16-member panel also expanded a climate rule that reduces carbon pollution with tradeable credits that gasoline and diesel producers must purchase from producers of lower-carbon fuels, such as hydrogen and biodiesel. By further incentivizing those cleaner technologies, the low-carbon fuel standard is expected to cut the cost of a new electric vehicle by up to $2,000 while raising gas prices by up to 36 cents over the next 12 years.